Mailinglist Archive: opensuse-virtual (14 mails)

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Re: [opensuse-virtual] correct IOMMU setup for AMD processor & xen pci passthrough?
  • From: "Jason Douglas" <jdouglas@xxxxxxxxxx>
  • Date: Thu, 13 Aug 2009 14:16:06 -0600
  • Message-id: <4A8420260200006F0006E493@xxxxxxxxxxxxxxxxxxxxxxx>
I'm pretty sure (85%) that iommu is off by default in xen 3.4, but even it for
some reason it's not, it would be a xen hypervisor option rather than a kernel
option that controls it. In order to enable it in xen 3.3, for example, you
need to pass iommu=1 on the hypervisor line, otherwise it is off.

Jason

On 8/13/2009 at 12:08 PM, in message
<94f2e81e0908131108s18872e2ajf093f78cab1a0871@xxxxxxxxxxxxxx>, PGNet Dev
<pgnet.dev+osvm@xxxxxxxxx> wrote:
hi,

i've an AMD processor,

cat /proc/cpuinfo | egrep "vendor|model|flags"
vendor_id : AuthenticAMD
model : 4
model name : AMD Phenom(tm) II X4 920 Processor
flags : fpu de tsc msr pae mce cx8 apic mtrr mca cmov
pat clflush
mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow
constant_tsc rep_good nopl pni cx16 popcnt lahf_lm cmp_legacy extapic
cr8_legacy abm sse4a misalignsse 3dnowprefetch

i've openSUSE 11.1, running latest SL111 kernel,

uname -ri
2.6.27.29-7-xen x86_64

with OBS Virtualization:Xen,

xm dmesg | grep "Xen version"
(XEN) Xen version 3.4.1_19711_01-9.1 (abuild@) (gcc version
4.3.2
[gcc-4_3-branch revision 141291] (SUSE Linux) ) Wed Aug 5 01:48:18
UTC 2009

i'm doing hardware passthrough of a sata PCI card to DomU, and want to
ensure iommu is (un)set properly. reading @,

"AMD64 specific boot options"
http://www.kernel.org/doc/Documentation/x86/x86_64/boot-options.txt

it seems i should (?) use,

iommu=off,noagp,noaperture

@ grub. however, comparing startup,


(1) WITH "iommu=off,noagp,noaperture" @ grub/menu.lst

dmesg | grep -i pciback
pciback 0000:04:07.0: seizing device
pciback 0000:04:07.0: enabling device (019d -> 019f)
pciback 0000:04:07.0: PCI INT A -> GSI 21 (level, low) -> IRQ 21
pciback 0000:04:07.0: PCI INT A disabled
pciback: vpci: 0000:04:07.0: assign to virtual slot 0
pciback 0000:04:07.0: enabling device (0080 -> 0083)
pciback 0000:04:07.0: PCI INT A -> GSI 21 (level, low) -> IRQ 21

(2) WITHOUT "iommu=off,noagp,noaperture" @ grub/menu.lst

dmesg | grep pciback
pciback 0000:04:07.0: seizing device
pciback 0000:04:07.0: enabling device (019d -> 019f)
pciback 0000:04:07.0: PCI INT A -> GSI 21 (level, low) -> IRQ 21
pciback 0000:04:07.0: PCI INT A disabled

i can see that there's a difference -- namely the,

pciback: vpci: 0000:04:07.0: assign to virtual slot 0

but in both cases, @ DomU, the card is correctly passed through,

lspci
00:00.0 RAID bus controller: Silicon Image, Inc. SiI 3124 PCI-X
Serial ATA Controller (rev 02)

and, afaict, works fine.

IS the aformentionted difference relevant? given my config, what is
the recommended IOMMU config for kernel cmd line?

thanks!


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